<!DOCTYPE html> <html> <head> <meta charset="UTF-8"> <title></title> </head> <body> <button class="btn">按钮</button> <script> var i=0; var btn=document.querySelector(".btn"); function on(ele,eventStr,callback){ if(ele.addEventListener){ ele.addEventListener(eventStr,callback); }else{ ele.attachEvent("on"+event,callback) } } function off(ele,eventStr,callback,n){ if(ele.removeEventListener){ ele.removeEventListener(eventStr,callback) }else{ ele.detachEvent("on"+eventStr,callback) } } function func(){ alert(i); i++; if(i>2){ off(btn,"click",func) } } on(btn,"click",func) </script> </body> </html>